Sports racquets, such as racquet ball racquets and tennis racquets, have evolved with the objective of improving their strength or power to hit a projectile, such as a ball or other propellable object such as a shuttlecock. The harder and faster a ball is hit and moves, the more difficult it is for an opponent to return the ball by hitting the ball accurately (if at all) with their racquet.
Older, conventional racquets are strung horizontally and vertically in a uniform manner from frame edge to frame edge to form a generally rectangular grid or string bed. Referring to FIG. 1, known non-long string racquets have between 75% and 86% of the length of their string beds or hitting surfaces covered by cross strings. This length is measured from the interior surface of the upper end of the frame of the racquet to the lower most cross string along the longitudinal axis. The string bed length is measured as the distance from the interior surface of the upper end of the frame along the longitudinal axis to an interior surface of the next-encountered, lower frame member.
Certain known aluminum racquets indicated with an * on FIG. 1 have an open throat piece where strings are present. A projectile, however, cannot access this area of these racquets and is not part of the hitting surface. Herein, the term string bed only refers to the hitting surface. These racquets are made with a frame member that begins with a substantially straight section, is curved outwardly and around the string bed, and terminates in a substantially straight section that is disposed close to or substantially parallel to the beginning straight section. The two straight sections (which are also used to form the racquet handle or shaft) are so close together that a projectile cannot get between them. For these racquets, the length of the hitting surface is given as the length along the longitudinal axis of the racquet from the inner surface of the top frame member to the point at which the beginning and ending racquet frame sections are no more than 0.25 inches apart. For tennis rackets, the frame sections are typically about 0.7 inches apart.
Cross strings are provided on the known racquets to brace the main strings laterally so that the impact of the ball on the strings does not push the main strings aside. This would cause a loss of energy while hitting the ball by causing motion of the strings in a direction parallel to the face of the racquet or string bed rather than perpendicular to the string bed as desired to transfer that energy to the ball.
In addition, when a ball is permitted to travel too far through the string bed by pushing the main strings aside, the trajectory of the ball from the string bed will be adversely affected, making it more difficult to control the direction of the ball.
Also for known strings that are used on racquets, the cross strings also help to absorb the impact forces reducing the force on any one string, which further reduces string breaks. Finally, cross strings may act to dampen vibration.
Cross strings on the string bed, however, constrain deflective movement of the main strings in a direction normal or perpendicular to the string bed. It has been found that the greater the deflection of the string, the greater the “dwell” time with the ball, which stores greater energy. This in turn causes a ball to be propelled from a racquet with more power and speed.
Instead of eliminating cross strings to gain this power, one improvement lengthens the strings instead. This is disclosed, for example, in U.S. Pat. No. 5,919,104 issued to Mortvedt et al., and which is entirely incorporated herein by reference. The '104 patent discloses that the vertical or main strings can be lengthened by wrapping an end of the strings around a pin inside the distal or far end of the handle. Thus, even though the string bed in such a racquet is about 15.5 inches long, the effective length of the main or “long” strings extending into the handle is about 22 inches. For tennis rackets, the effective lengths for long strings are about 27 to 28 inches.
It can be seen from the known racquets that eliminating any major number of cross strings was simply not considered a realistic option. Thus, removing all cross strings has never been considered at all.